Correos en VBasic

Antes que nada da de alta la libreria Microsoft MAPI Controls y checa la rutina siguiente:
Private Function EnviarCorreo(ByVal Tema As String, ByVal Email As String, ByVal Texto As String, ByVal Llave As String) As Date
Dim Receptores() As String, X As Long, Temp
ReDim Receptores(0 To 0)
EnviarCorreo = Si
'MAPI constants from CONSTANT.TXT file:
Const SESSION_SIGNON = 1
Const MESSAGE_COMPOSE = 6
Const ATTACHTYPE_DATA = 0
Const RECIPTYPE_TO = 1
Const RECIPTYPE_CC = 2
Const MESSAGE_RESOLVENAME = 13
Const MESSAGE_SEND = 3
Const SESSION_SIGNOFF = 2
MAPISession.LogonUI = No
On Error Resume Next
MAPISession.Action = mapSignOn 'SESSION_SIGNON
If Val(Err.Number) <> 32050 And Err.Number <> 0 Then
'*** Atrapado de Errores
JLLog "Error: Al intentar enviar el correo, se produjo el error " + Format(Err.Number) + ") " + Err. Description
EnviarCorreo = No
Exit Function
End If
On Error GoTo 0
MAPIMessages.SessionID = MAPISession.SessionID
MAPIMessages.Action = MESSAGE_COMPOSE 'Start a new message
MAPIMessages.MsgSubject = Tema + " {" + Llave + "}"
MAPIMessages.MsgNoteText = Texto
'Separar Recipients
Temp = 0
For X = 1 To Len(Email)
If Mid(Email, X, 1) = ";" Then Temp = Temp + 1
Next
ReDim Receptores(0 To Temp)
Temp = Email
X = -1
Do While InStr(1, Temp, ";") > 0
X = X + 1
Receptores(X) = Left(Temp, InStr(1, Temp, ";") - 1)
MAPIMessages.RecipIndex = X 'First recipient
MAPIMessages.RecipType = RECIPTYPE_TO 'Recipient in TO line
MAPIMessages.RecipDisplayName = Receptores(X) 'e-mail name
MAPIMessages.MsgReceiptRequested = True
Temp = Trim(Mid(Temp, InStr(1, Temp, ";") + 1))
Loop
X = X + 1
Receptores(X) = Trim(Temp)
'Set the recipients
MAPIMessages.RecipIndex = X 'First recipient
MAPIMessages.RecipType = RECIPTYPE_TO 'Recipient in TO line
MAPIMessages.RecipDisplayName = Receptores(X) 'e-mail name
MAPIMessages.MsgReceiptRequested = True
On Error Resume Next
MAPIMessages.Action = MESSAGE_RESOLVENAME
If Err.Number <> 0 Then
EnviarCorreo = No
JLLog "Error: Al intentar enviar el correo, se produjo el error " + Format(Err.Number) + ") " + Err. Description
JLLog "El correo va dirigido a: " + Email
JLLog Format(UBound(Receptores)) + " receptores de correo"
Exit Function
End If
On Error GoTo 0
MAPIMessages.Action = MESSAGE_SEND
MAPISession.Action = SESSION_SIGNOFF
End Function